EXCHANGE 


EXCHANGE 


The  Preparation,  Properties, 

and  Composition  of 

Silundum 


DISSERTATION 

SUBMITTED  IN  PARTIAL  FULFILMENT  OF  THE  REQUIRE- 
MENTS FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY, 
IN  THE  FACULTY  OF  PURE  SCIENCE,  OF 
COLUMBIA  UNIVERSITY 


OF  THE  s^ 

UNIVERSITY 
o         OF 


BY 

ALEXANDER  LOW,  B.S.,  M.A. 

NEW  YORK  CITY 
1915 


The  Preparation,  Properties, 

and  Composition  of 

Silundum 


DISSERTATION 

SUBMITTED  IN  PARTIAL  FULFILMENT  OF   THE   REQUIRE- 
MENTS FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY, 
IN  THE  FACULTY  OF  PURE  SCIENCE,  OF 
COLUMBIA  UNIVERSITY 


BY 

ALEXANDER  LOWY,  B.S.,  KLA. 

NEW  YORK  CITY 
1915 


TABLE  OF  CONTENTS 


Acknowledgment 4 

Introductory  and  Historical 5 

Preparation  of  Silundum ! 9 

Diagram  of  Furnace 9 

Description  of  Experiments 10 

Summary  of  Experiments 13 

Properties  of  Silundum 14 

Composition  of  Silundum 17 

Summary 22 

Bibliography 23 

Vita 24 


TP 


ACKNOWLEDGMENT 

The  author  wishes  to  take  this  opportunity  to  thank  » 
Professor  S.  A.  Tucker,  at  whose  suggestion  this  work 
was  undertaken,  for  his  kind  interest  and  advice. 

The  author  also  wishes  to  express  his  sincere  grati- 
tude to  Prof.  H.  T.  Beans  for  valuable  suggestions. 

ALEXANDER  LOWY 

ELECTRO-CHEMICAL  LABORATORY 

HAVEMEYER  HALL,  COLUMBIA  UNIVERSITY 

April,  1915 


THE  PREPARATION,  PROPERTIES  AND  COMPOSITION 
OF  SILUNDUM 

By  ALEXANDER  LOWY 

Silundum  is  a  product  of  the  electric  furnace,  and 
was  discovered  by  Boiling,1  at  Frankfort-on-the- 
Main,  Germany.  As  early  as  1900  he  began  the  study 
of  the  use  of  the  various  silicon  carbides  as  resistors, 
being  led  to  this  work  by  the  fact  that  these  carbides 
can  be  subjected  to  high  temperatures  without  under- 
going decomposition.  His  method  was  to  mix  the 
silicon  carbide  powder  with  various  binders  in  order 
to  hold  the  individual  particles  together.  The  mass 
is  a  non-conductor  at  low  temperatures,  but  at  about 
700-800°  C.  it  becomes  conductive,  thus  being  use- 
less at  a  higher  temperature. 

By  1904  a  process  was  worked  out  and  patented 
by  which  it  is  possible  to  convert  any  piece  of  carbon, 
e.  g.,  a  crucible,  brick,  rod,  etc.,  into  silicon  carbide. 
By  this  method  resistors  without  any  binding  ma- 
terial are  obtained,  which  will  stand  temperatures 
as  high  as  1650-1700°  C.  Previous  to  1904,  silicon 
carbide  had  been  known  in  two  conditions  only — 
amorphous  and  crystalline — and  it  was  supposed  to 
be  formed  by  the  interaction  of  sublimed  carbon  and 
sublimed  silicon.  Boiling,  however,  discovered  that 
silicon  penetrates  carbon  when  both  are  in  a  highly 
heated  condition,  but  at  too  low  a  temperature  for 
the  carbon  to  have  any  appreciable  vapor  tension. 
He  claimed  that  silicon  at  about  1600°  C.  exists  in 
the  form  of  vapor.  Carbon  at  this  temperature  has 
an  extremely  small  vapor  pressure.  According  to 
Boiling's  definition,  silundum  is  the  product  that  is 
obtained  when  carbon  is  heated  in  an  atmosphere  of 
silicon  vapor. 

An  electric  furnace  such  as  is  used  for  the  manu- 
facture of  carborundum  was  used  for  the  preparation 
of  silundum.  Pieces  of  carbon  pressed  to  the  desired 
shape  were  introduced  into  a  mixture  of  sand  and 

1  F.  Boiling,   Chem.  Ztg.,  32,    1 104;  Electrochem.  and  Met.  Ind.,  7,  24 

314193 


carbon,  nnc  tins  was  heated  by  using  as  a  resistor  a 
granular  core  of  coke.  The  sand  was  reduced  and  the 
silicon,  volatilizing,  penetrated  the  carbon  objects 
and  thus  "silundumized"  them. 

Moyat1  criticized  Boiling's  work,  and  claimed  that 
silundum  Was  not  a  new  chemical  individual,  but 
merely  a  new  variety  of  silicon  carbide. 

Acheson's  patent2  No.  895,531  is  interesting,  inas- 
much as  it  deals  with  a  similar  product.  In  order 
to  protect  crucibles,  tuyeres,  bricks,  muffles,  and 
other  articles  of  carbon  from  destruction  at  high  tem- 
peratures in  the  presence  of  oxygen,  or  when  exposed 
to  molten  metals,  Acheson  proposes  to  cover  them 
with  a  coating  of  a  highly  refractory  siloxicon,  or 
silicon  oxycarbide.  This  prolongs  their  life  and  pre- 
vents disintegration.  A  portion  of  the  carbon  on  the 
surface  of  the  article  itself  is  utilized  in  producing  the 
siloxicon  coating.  After  having  been  shaped  to  the 
form  desired,  the  carbon  or  graphite  article  is  em- 
bedded in  a  mixture  of  silica  and  carbon  in  the  pro- 
portion of  two  parts  of  sand  to  five  of  carbon,  and  is 
exposed  to  the  proper  temperature  at  which  silicon, 
oxygen,  and  carbon  combine  to  form  siloxicon. 

The  product  obtained  by  this  method  resembles 
in  appearance  the  lighter-colored  silundum,  which 
is  to  be  discussed  later  in  greater  detail. 

Tucker  and  his  co-workers3  in  1909  made  an  experi- 
mental study  of  the  formation  of  silundum.  In 
their  experiments  the  charge  was  made  up  according 
to  the  proportion  Si02  :  2SiC.  This  charge  was 
heated  in  a  carborundum  furnace,  the  core  of  which, 
instead  of  being  of  granular  carbon,  consisted  of  a 
number  of  small  carbon  plates,  pressed  together  be- 
tween two  horizontal  graphite  electrodes.  Around 
the  core  was  placed  a  charge  of  sand  and  carborun- 
dum, in  which  were  embedded,  at  varying  distances 
from  the  core,  the  carbon  articles  to  be  silundumized. 
These  workers  also  investigated  the  reactions  between 
sand  and  carbon.  Their  experiments  showed  that 
silundum  can  be  produced  by  either  of  the  above  re- 
actions, *".  e.,  by  the  reaction  of  sand  and  carbon  or 
of  sand  and  carborundum.  They  also  showed  the  rela- 
tive difficulty  of  oxidizing  silundum.  Two  plates, 
silundurnized  on  the  surface,  were  heated  to  a  high 
temperature  by  means  of  an  electric  current.  The 

1  Moyat.  Chem.  Ztg..  32,  1166. 

2  Acheson,  U.  S.  Patent  No.  895,531;  Electrochem.  and  Met.  Ind..  6,  379 
*  Ttfcker,  Kudlich  and  Heumann,  Trans.  Am.  Electrochem.  Soc.,  16,  207- 

(6) 


graphite  cores  were  completely  oxidized,  leaving  only 
box-like  shells  of  silundum. 

Amberg-Bodio1  also  prepared  silundum, t  and  states 
that,  "According  to  the  temperature  and  the  time, 
there  is  obtained  a  gray-  to  metallic-appearing  silicon 
carbide,  with  a  content  of  silicon  greater  or  less  than 
that  which  corresponds  to  the  formula  SiC.  The 
process  may  be  interrupted  at  any  time  and  a  coating 
of  silundum  of  any  desired  thickness  produced." 

Within  the  past  few  years,  F.  J.  Tone2  has  ob- 
tained four  patents  for  the  preparation  and  manufac- 
ture of  dense,  compacted  silicon  carbide.  From  his 
description,  the  term  "dense  compacted  silicon  car- 
bide" is  synonymous  with  the  term  "silundum." 

Egly,3  early  in  1913,  patented  a  substance  called 
"Silit"  which  is  prepared  by  heating  to  a  fairly  high 
temperature  silicon  carbide,  silicon,  and  a  binder, 
until  a  homogeneous  mass  results.  "Silit"  is  a  good 
resistor  and  has  many  industrial  applications. 

F.  J.  Tone4  describes  a  silicidized  carbon  which 
he  calls  "Silfrax."  In  order  to  show  the  interior 
structure  of  the  material,  he  gives  microphotographs 
of  it. 

A  survey  of  the  literature  and  a  careful  preliminary 
examination  of  several  samples  of  silundum,  indicated 
to  the  writers  that  in  all  probability  the  material 
known  as  silundum  exists  in  two  modifications.  The 
crudeness  of  the  analytical  methods  used  in  determin- 
ing the  composition  of  these  refractory  materials 
made  it  impossible  to  draw  any  definite  conclusion 
from  the  work  already  published.  Moreover,  little 
or  no  data  are  available  on  such  important  conditions 
for  the  preparation  of  silundum  as  temperature, 
proportions  of  reacting  materials,  and  time  of  heating. 
It  seemed,  therefore,  that  by  a  careful  investigation 
into  the  best  conditions  of  temperature  for  preparing 
silundum,  with  an  improved  method  of  analysis  and 
a  careful  examination  of  properties,  considerable 
light  might  be  thrown  upon  the  question  of  the  com- 
position of  silundum.  With  this  purpose  in  mind  the 
present  investigation  was  undertaken. 

Silundum,  according  to  the  conditions  under  which 
it  is  formed,  exists  in  two  modifications.  One  of  these, 

1  Amberg-Bodio,   Z.    Elektrochem.,    15,   725-727;   Chem.    Abs.,    4,    149. 

2  Tone,    U.    S.    Patents   Nos.    913,324,    992,698,    1,013,700,    1,013,701. 

3  Egly.  Elektrotechn.  Zeit.,  34,  263-267;  Chem.  Abs.,  6,  536;  7,   1142, 
2357. 

*  Tone.  Trans.  Am.  Electrochem.  Soc.,  26,  181. 

(7) 


a  steel-gray  variety,  is  formed  at  a  temperature  of 
about  1900°  C.  and  analyzes  very  closely  to  the  formula 
SiC;  the  other,  a  slate-green  variety  formed  at  about 
1600°  C.,  is  an  oxycarbide  of  silicon  of  the  formula 
Si4C40.  It  has  been  determined  that  silundum  does 
not  decompose  below  2200°  C.  At  higher  tempera- 
tures silicon  distils  off,  leaving  a  graphite  skeleton 
of  the  same  form  as  the  original  silundum,  which 
action  would  indicate  that  the  graphite  does  not 
vaporize  at  the  temperature  of  decomposition,  and 
would  show,  further,  that  silundum  is  formed  by  the 
reaction  of  silicon  vapor  and  solid  carbon,  the  tempera- 
ture of  formation  being  lower  than  the  temperature 
of  decomposition. 

The  action  which  takes  place  in  the  process  of 
silundumization  may  be  summarized  as  follows: 
The  silicon  which  is  liberated  from  silica  by  the  re- 
ducing action  of  coke-  or  sugar-carbon  penetrates 
the  solid  carbon  or  graphite  objects,  and  there  reacts 
with  the  carbon,  forming  a  steel-gray  variety  of  sil- 
undum. This  takes  place  above  1800°  C.  Below 
this  temperature  the  slate-green  variety  is  formed, 
most  likely  by  the  penetration  of  the  carbon  by  the 
silicon  vapor  and  carbon  monoxide. 

The  stumbling  block  in  the  analysis  of  such  refrac- 
tory substances  as  silundum  has  been  the  difficulty 
of  completely  decomposing  the  material  and  burning 
all  the  carbon  to  carbon  dioxide.  The  silicon  may  be 
determined  easily  by  means  of  the  well-known  sodium 
carbonate  and  potassium  nitrate  fusion.  In  order, 
therefore,  to  overcome  the  difficulties  hitherto  en- 
countered in  the  carbon  determination,  various  fluxes 
and  oxidizing  agents  were  tried,  with  the  object  of 
replacing  the  inadequate  sodium  peroxide  and  mag- 
nesia method1  previously  used.  After  considerable 
experimentation  litharge  was  found  to  be  an  excellent 
flux  for  decomposing  the  material  and  partially  oxidiz- 
ing it,  complete  oxidation  being  effected  by  means  of 
a  stream  of  oxygen.  Using  this  method  on  car- 
borundum crystals,  results  were  obtained  that  were 
accurate  within  0.3  per  cent  of  theoretical.  Con- 
sidering the  nature  of  the  material  treated,  this  was 
satisfactory.  Analyses  of  silundum  samples  were 
made  by  this  new  method,  and  the  results  checked 
on  duplicates.  Therefore,  we  consider  this  to  be 
a  good  method  for  the  accurate  determination  of 
carbon  in  refractory  carborundum-like  substances. 

1  Fitzgerald,  Electrochem.  Ind.,  2,  443. 
(8) 


DESCRIPTION    OF    EXPERIMENTS 

PREPARATION  OF  siLUNDUM — In  order  to  obtain 
sufficient  amounts  of  the  substance  for  t'he  further 
study  of  its  properties  and  composition,  silundum 
was  prepared  in  a  coke  resistance  furnace  (Experi- 
ments i  to  7).  Since  this  type  of  furnace  does  not 
lend  itself  to  accurate  temperature  measurements, 
the  temperatures  of  formation  and  decomposition 
were  measured  in  a  separate  series  of  experiments 
(8  to  13)  in  the  Arsem  vacuum  electric  furnace.1 


FIG.  1 — RESISTANCE  FURNACE  (DIMENSIONS  IN  MMS.) 

The  coke  resistance  furnace2  was  chosen  because 
with  it  a  range  of  temperatures  up  to  about  2600°  C. 
can  be  obtained  by  varying  the  amount  of  electrical 
energy.  The  furnace,  diagrammatically  represented 
in  Fig.  i,  consists  essentially  of  a  coke  resistor  en- 
closed by  cemented  fire-clay  brick  walls  with  magnesia 
lining.  The  graphite  electrodes  extend  through  the 
walls  into  the  coke. 

The  graphite  crucible  containing  the  charge  and 
the  articles  to  be  silundumized  were  embedded  in 
the  coke  core.  The  energy  was  supplied  by  a  50 

1  Arsem,  Trans.  Am.  Electrochem.  Soc.,  9,  153. 

2  Tucker,  Ibid.,  11,  307. 

(9) 


kw.  A.  C.  generator.  The  measurements  and  the 
exact  details  of  construction  of  the  furnace  are  indi- 
cated in  the  diagram. 

Carbon  and  graphite  rods  varying  in  diameter 
from  1/g  to  3/8  in.,  and  2  in.  in  length  were  used.  In 
a  few  experiments  carbon 'tubes  were  used.  The 
charge  consisted  of  clean  sand  and  coke.  For  the 
samples  that  were  to  be  analyzed,  special  charges, 
consisting  of  precipitated  silica  and  sugar-carbon 
were  used,  in  order  to  obtain  a  pure  product.  The 
objects  to  be  silundumized  in  these  cases  were  also 
made  of  graphite  of  the  highest  purity. 


EXPERIMENTS    IN    COKE    RESISTANCE    FURNACE 

Experiments  i  to  7  were  conducted  in  order  to 
find  out  how  the  variation  of  the  different  factors 
of  time,  energy  consumption  and  composition  of 
charge  would  affect  the  nature  of  the  product  formed. 
The  readings  taken  during  these  experiments  appear 
in  Table  I. 

TABLE  I — READINGS  TAKEN  DURING  EXPERIMENTS  IN   COKE   RESISTANCE 


EXPERIMENT  No.  3 
Time     Amperes  Volts 


FURNACE 

EXPERIMENT  No.   1 

EXPERIMENT  No.  2 

Time 

Amperes 

Volts 

Time  Ai 

nperes 

Volts 

10.00 

0 

40 

1.30 

0 

35 

10.10 

75 

38 

1.45 

200 

30 

10.20 

100 

36 

1.55 

300 

30 

10.30 

150 

34 

2.00 

400 

30 

10.40 

150 

34 

2.10 

400 

26 

10.50 

150 

34 

2.20 

400 

26 

11.00 

200 

28 

2.30 

400 

26 

11.10 

270 

26 

2.40 

410 

26 

11.20 

300 

26 

2.50 

410 

26 

11.30 

300 

26 

3.00 

410 

26 

12.00 

300 

26 

Time 
9.55 
10.05 
10.10 
10.15 
10.20 
10.25 
10.30 
10.35 
10.40 
10.45 


EXPERIMENT 
Amperes  Volts 


0 
75 
100 
200 
250 
350 
450 
550 
550 
550 


35 
34 
SO 
29 
30 
29 
28 
28 
28 
28 


NUMBER  5 

Time  Amperes  Volts 

10.50       550  28 

10.55        525  28 

11.00       550  28 

11.05        550  28 

11.15        555  28 

11.25        550  28 

11.35        550  28 

11.45        550  28 

11.55        550  28 

12.00       550  28 


9.30 

0 

34 

9.45 

200 

32 

9.55 

310 

30 

10.00 

405 

25 

10.15 

400 

25 

10.30 

410 

25 

10.45 

410 

25 

11.00 

400 

25  . 

11.30 

400 

25 

12.00 

400 

25 

12.30 

400 

25 

1.00 

400 

25 

EXPERIMENT  No.  7 

Time 

Amperes 

Volts 

10.00 

0 

40 

10.10 

100 

36 

10.20 

200 

30 

10.30 

500 

28 

10.40 

500 

26 

10.50 

550 

25 

11.00 

650 

25' 

11.  10 

650 

25 

11.30 

650 

25 

12.00 

650 

25 

12.30 

650 

25 

EXPERIMENT  i — A  charge  consisting  of  a  mixture 
of  60  g.  coke  and  150  g.  sand  (the  theoretical  amount 
to  produce  silicon)  was  placed  in  a  graphite  crucible. 
Four  carbon  rods  1/4  in.  in  diameter  and  2  in.  long  were 
then  embedded  in  the  charge  and  the  crucible  tightly 
covered  with  a  graphite  cover.  Crucible  and  con- 
tents were  placed  in  the  furnace  within  the  coke  re- 
sistor, and  the  electric  current  turned  on.  Atter  two 
hours  the  furnace  was  allowed  to  cool,  and  examina- 

(10) 


tion  of  the  contents  of  the  crucible  showed  that  the 
rods  were  not  silundumized.  The  sand  was  fused 
around  the  graphite  rods.  This  experiment  indicated 
that  a  higher  temperature  was  necessary  for  the  ac- 
complishment of  the  desired  reaction. 

EXPERIMENT  2  was  conducted  in  order  to  study 
the  effect  of  higher  temperature  on  the  reaction. 
The  electrical  energy  consumption  was  increased,  as 
indicated  above,  with  the  object  of  obtaining  this 
desired  higher  temperature.  The  composition  of  the 
charge  was  the  same  as  in  Experiment  i.  The  graphite 
rods  upon  fracture  were  found  to  be  silundumized 
half  way  through.  The  line  of  demarcation  between 
the  silundumized  portion  and  the  portion  not  acted 
upon  was  very  sharp  (see  the  microphotograph, 
Fig.  2).  The  color  of  this  product  was  slate-green. 

EXPERIMENT  3  was  intended  to  produce  silundum 
extending  through  the  entire  cross-section  of  the  rods. 
The  charge  was  made  up  exactly  as  in  Experiment  i, 
and  the  temperature  conditions  were  also  duplicated 
as  closely  as  possible.  This  experiment,  however, 
was  carried  on  two  hours  longer  than  Experiment  2. 
The  rods  were  completely  silundumized,  and  no  graph- 
ite core  was  visible.  The  color  of  the  rods  was  slate- 
green.  They  were  conductors  of  electricity  even  at 
ordinary  temperatures.  f 

EXPERIMENT  4  was  carried'  out  in  order  to  determine 
whether  there  is  any  difference  in  the  nature  of  the 
product  obtained  when  the  rods  are  embedded  in  the 
charge  and  when  they  are  exposed.  The  charge  in 
this  experiment  consisted  of  120  g.  silica  and  48  g. 
coke.  The  rod  was  placed  in  the  charge  with  the  upper 
half  extending  above  the  surface  of  the  charge.  The 
other  conditions  of  the  experiment  were  the  same  as 
in  Experiment  2.  The  product  was  of  a  slate-green 
color.  Fracture  showed  that  the  part  embedded  in 
the  charge  was  silundumized  about  half  way  through, 
while  the  part  exposed  had  only  a  superficial  coating 
of  silundum.  This  experiment  shows  that  more  com- 
plete silundumization  takes  place  when  the  rods  are 
embedded  in  the  charge  than  when  they  are  exposed. 

EXPERIMENT  5  was  intended  to  show  the  effect  of 
still  higher  temperatures  than  were  used  in  the  previous 
experiments.  A  charge  like  that  in  Experiment  i 
was  used.  The  rods  upon  fracture  were  found  to  be 
silundumized  about  half  way  through.  The  color 
of  the  product  was  steel-gray,  resembling  carborundum. 
Clearly  defined  characteristic  carborundum  crystals 

(n) 


were  found  on  the  surfaces  of  the  silundumized  rods. 
EXPERIMENT  6  was  similar  to  Experiment  5  except 
that  the  heating  was  carried  on  for  four  hours.  Subse- 
quent examination  of  the  rods  showed  that  complete 
silundumization  had  taken  place.  The  rods  were 
steel-gray  in  color,  and  had  small  carborundum  crys- 


FIG.  2. 


tals  on  the  surface.  They  were  conductors  of  elec- 
tricity even  at  ordinary  temperatures. 

EXPERIMENT  j  was  designed  to  study  the  effect  of 
high  temperatures.  A  rod  of  silundum  of  the  steel- 
gray  variety  was  placed  in  the  graphite  crucible  and 
heated  for  two  hours  under  electrical  conditions  as 
given  in  Table  I.  The  silundum  rod  was  found  to 
have  lost  all  its  characteristic  properties,  and  on  fur- 
ther examination  proved  to  be  graphite. 

Experiments  were  also  carried  out  in  order  to  de- 
termine what  would  be  the  effect  of  varying  the  compo- 
sition of  the  charge  used.  It  was  found,  however, 
that  no  appreciable  difference  in  the  nature  of  the  prod- 
uct resulted  from  such  variation.  Some  of  the  sand 
in  the  charge  sinks  to  the  bottom,  and  the  coke,  be- 
cause of-  its  lower  specific  gravity,  remains  at  the  top. 
There  is  never,  therefore,  any  very  intimate  mixture 
of  the  ingredients.  It  is  not  surprising,  in  consequence, 
that  small  differences  in  the  ratio  of  the  components  of 
the  charge  should  produce  no  differences  in  the  results. 

(12) 


EXPERIMENTS     IN     ARSEM     ELECTRIC     VACUUM     FURNACE 

EXPERIMENTS  8  TO  13 — As  temperature  determina- 
tions cannot  be  made  with  any  degree  of  accuracy 
in  the  electric  furnace  used  above,  Experiments  8 
to  13  were  carried  out  in  an  Arsem  electric  vacuum 
furnace,1  in  order  to  determine  the  temperature  of 
formation  and  decomposition  of  silundum.  Details 
of  the  construction  of  this  furnace,  which  is  complex, 
are  out  of  place  in  this  article,  and  the  reader  is  re- 
ferred to  the  reference  below.  The  temperature  was 
measured  with  a  Wanner  optical  pyrometer.  As* 
pyrometer  readings  are  untrustworthy  in  the  pres- 
ence of  fumes,  blank  runs  were  first  made  without  any 
material  in  the  furnace,  noting  at  the  same  time  the 
energy  consumed  and  the  temperature  attained.  These 
temperatures  were  then  taken  as  the  temperatures 
which  would  exist  in  the  experiments  made  under 
the  same  conditions  of  time  and  energy  consumed. 

A  graphite  crucible,  3/4  in.  diameter  and  2*/2  in. 
high,  was  used.  The  carbon  rod  to  be  silundumized 
was  placed  in  the  center  of  this  crucible  and  was  sur- 
rounded with  the  charge,  composed  as  usual  of  silica 
and  coke.  The  energy  consumption  was  recorded  by 
a  wattmeter.  The  results  of  these  experiments  are 
given  in  Table  II. 

TABLE  II — RESULTS  OP  EXPERIMENTS  IN  ARSEM  ELECTRIC  VACUUM* 
FURNACE 


Ratio  of 

Exp. 

Temp. 

SiCh  to  C 

Color  of 

No. 

0  C. 

in  charge 

product 

Remarks 

8.... 

.      1300 

30      12 

No  silundum  formed 

9  

.      1606 

30 

12 

Slate-green 

Surface  silundumization 

10.... 

.      1712 

30 

12 

Slate-green 

Surface  silundumization 

11.... 

.      1845 

30 

12 

Steel-gray 

|  Surface    silundumization  — 

12.... 

.      1900 

30 

12 

Steel-gray 

I      most  of  charge  volatilized 

13.... 

.      Over  2200 

30  :   J2 

Product  decomposed 

Owing  to  the  fact  that  a  high  vacuum  was  main- 
tained as  the  temperature  rose,  some  of  the  silicon 
distilled  from  the  charge  and  the  depth  of  silundumiza- 
tion was  very  small,  but  the  surface  layer  was  suffi- 
ciently characteristic  to  determine  the  nature  of  the 
product. 

CONCLUSIONS    PROM    EXPERIMENTS 

I — The  temperature  of  formation  of  silundum  is 
above  1300°  C.  (see  Expts.  i  and  8). 

II — Up  to  about  1800°  C.  the  greenish  slate-colored 
variety  of  silundum  is  formed  (see  Expts.  2,  3,  4,  9  and 
lo). 

Ill — Above  1800°  C.  the  steel-gray  colored  variety 
of  silundum  is  formed  (see  Expts.  5,  6,  n  and  12). 

1  Arsem,  Trans.  Am.  Electrochem.  Soc.,  9,  153. 
(13) 


IV — Continued  heating  above  2200°  C.  results  in 
decomposition  of  the  silundum  with  formation  of 
graphite  (see  Expts.  7  and  13). 

V — The  extent  ,  of  penetration  of  silundumization 
depends  upon  the  duration  of  heating  (see  Expts. 
2,  3,  4,  5  and  6). 

VI — More  complete  silundumization  takes  place 
when  the  object  is  embedded  in  the  charge  (see  Expt.  4) . 

PROPERTIES    OF    SILUNDUM 

According  to  Boiling,1  silundum  is  a  form  of  silicon 
carbide,  and  possesses  properties  similar  to  those  of 
carborundum.  It  is  capable  of  being  maintained 
for  a  long  time  at  temperatures  up  to  1600°  C.  without 
change,  and  may  be  heated  for  a  short  time  to  1700°  C. 
without  deterioration.  It  is  a  conductor  of  elec- 
tricity, its  resistance  being  about  six  times  that  of 
carbon.  At  1000°  C.  its  resistance  is  one-half  to  two- 
thirds  of  that  at  room  temperature.  The  electrical 
resistance  is  variable,  and  depends  upon  the  variety 
and  hardness  of  the  carbon  used  in  the  preparation, 
that  made  from  porous  carbon  having  a  higher  resis- 
tance than  that  made  from  compact.  Silundum  can- 
not be  melted;  in  this  respect  it  resembles  carbon. 
It  may  be  nickel-plated,  or  covered  with  a  layer  of 
platinum.  It  is  a  refractory  material,  but  it  is  attacked 
by"  molten  metals  at  high  temperatures.  It  may  be 
heated  to  a  white  heat  and  plunged  into  cold  water 
without  cracking. 

Briefly,  the  results  of  the  present  investigation  of 
the  physical  and  chemical  properties  of  silundum 
may  be  summarized  as  follows: 

i — Silundum  is  a  good  conductor  of  electricity, 
with  a  negative  temperature  coefficient  for  its  resistance. 

2 — Silundum  is  a  very  hard  substance — with  a  hard- 
ness on  Mohr's  scale  of  about  9. 

3 — The    specific    gravity    of    silundum    is    2.9    to    3. 

4 — Silundum  is  not  attacked  by  hydrogen,  oxygen, 
or  nitrogen  even  at  1100°  C. 

5 — Silundum  is  attacked  by  some  fused  salts. 

6 — Silundum  is  not  attacked  by  acids. 

ELECTRICAL  CONDUCTIVITY — The  following  is  the 
method  for  determining  the  electrical  conductivity 
of  silundum:  A  cylindrical  rod  of  uniform  diameter 
was  used.  In  order  to  diminish  the  contact  resistance 
as  much  as  possible  the  ends  were  copper-plated, 
thus:  the  rods  were  dipped  into  paraffine,  the  ends 

1  Boiling,  Loc.  cit. 

(14) 


craped  clean,  coated  with  a  very  thin  layer  of  graphite, 
and  then  copper-plated  electrolytically.  Copper  wires 
were  soldered  on,  and  the  rods  were  deaned.  The 
resistance  was  determined  at  various  temperatures 
with  a  very  accurate  Wheatstone  bridge.1 

The  rod  of  the  slate-green  variety  was  1.871  cm. 
long  and  0.635  cm.  in  diameter.  The  rod  of  the  steel- 
gray  variety  was  2.078  cm.  long  and  0.348  cm.  in  di- 
ameter. Owing  to  the  fusion  of  the  solder,  measure- 
ments could  not  be  made  above  225°  C.  The  rods 
were  heated  in  a  small  Hoskins  electric  furnace,  and 


TABLE 

III  —  RESISTANCES  OF  THE  Two 

VARIETIES  OF  SILUNDUM 

SLATE-GREEN  VARIETY 

STEEL-GRAY  VARIETY 

Rod  1.871  Cm.  Long  and 

Rod  2.078  Cm.  Long  and 

0.635  Cm.  in  Diameter 

0.348  Cm.  in  Diameter 

Temp. 

Measured            Specific 
resistance          resistance 

Measured           Specific 
resistance          resistance 

0  C. 

Ohms          Ohms  per  cc. 

Ohms          Ohms  per  cc. 

20 

0.91450              0.1546 

5.2250              0.2391 

25 

0.91270              0.1543 

5.1886              0.2374 

50 

0.90000              0.1522 

4.9786              0.2278 

75 

0.89092              0.1506 

4.8186              0.2205 

100 

0.88192              0.1491 

4.6291              0.2118 

125 

0.87212              0.1474 

4.4191              0.2022 

150 

0.86202              0.1457 

4.2791               0.1958 

175 

0.85392              0.1443 

4.1541              0.1901 

200 

0.84522              0.1429 

4.0441              0.1850 

225 

0.83530              0.1412 

3.9541              0.1809 

the  temperature  was  read  by  means  of  an  ordinary 
thermometer  with  its  bulb  in  the  heating  chamber. 
Table  III  shows  the  measured  resistances  and  the 
specific  resistances  in  ohms  at  the  various  tempera- 
tures. The  specific  resistances  are  plotted  against  the 
temperatures  in  Fig.  3. 

Attempts  were  made  to  spray  the  ends  of  the  rods 
according  to  the  Schoop2  method,  but  when  they  were 
heated,  the  brass  contacts  became  loosened  from  the 
ends  of  the  rods. 

It  is  evident  from  the  above  results  that  .the  re- 
sistance is  practically  a  linear  function  of  the  tempera- 
ture. The  temperature  coefficient  of  resistance  is 
negative.  The  specific  resistance  is  much  less  than 
that  for  carborundum,  being,  at  25°,  0.1543  ohm 
per  cubic  centimeter  for  the  slate-green  variety,  and 
0.2374  ohm  per  cubic  centimeter  for  the  steel-gray 
variety,  while  that  of  carborundum  is  50  ohms  per 
cubic  centimeter  at  25°.3 

It  was  attempted  to  measure  the  ohmic  resistance 
of  the  above  rods  at  higher  temperatures  by  clamping 
them  between  platinum  plates.  The  resistance  varied 

1  This  was  done  in  the  Electrical  Testing  Laboratory  of  Columbia 
University. 

»  Met.  Ind.,  1914,  p.  457.     THIS  JOURNAL,  4,  853;  5,  776;  7,  72. 

3  Pamphlet,  "Chemical  and  Physical  Properties  of  Carborundum," 
published  by  The  Carborundum  Co.,  Niagara  Falls,  N.  Y.,  1913. 

(15) 


from  75  ohms  to  a  fraction  of  an  ohm,  depending  upon 
the  pressure  exerted  upon  the  platinum  plates,  so  that 
measurements  of  the  same  order  of  accuracy  as  those 
determined  above  with  plated  ends  could  not  be  made 
above  225°  C. 

HARDNESS  and  specific  gravity  measurements  are 
given  in  Table  IV  for  the  two  varieties  of  silundum 
and  for  Tone's  and  Boiling's  products. 

SPECIFIC  GRAVITY  was  determined  by  means  of  a 
specific  gravity  bottle,  care  being  taken  to  expel  all  air 
bubbles  by  careful  heating  and  subsequent  cooling. 


•c. 

IZ5 

200 
175 


/25 
400 


5o 


25 


OHMS 


PER 


S.L 


CUBIC 


ICE 


CENTI>ETER 


•/8o     -190 

FIG.  3 


•Zoo    -2/0      Z2.0     .£30    -240 


TABLE  IV — HARDNESS  AND  SPECIFIC  GRAVITY  OF  SILUNDUM 


Specific  gravity 

Tone's  "Silifrax" 2.96 

Boiling's  silundum 2.97 

Greenish  variety  silundum 2 . 92 

Steel-gray  variety  silundum 2 . 94 


Hardness 
(Mohr's  scale) 
9  plus 
9 

8  to  9 

9  minus 


PROPERTIES    OF    BOTH    VARIETIES    OF    SILUNDUM 

ACTION  OF  GASES — Oxygen,  nitrogen,  and  hydrogen 
have  no  action  on  silundum  heated  to  temperatures 
up  to  1100°  C.  An  attempt  was  made  to  oxidize  silun- 
dum in  a  bomb  calorimeter  under  a  pressure  of  25 
atmospheres  of  oxygen,  in  a  gelatine  capsule  con- 
taining a  mixture  of  benzoic  acid  and  silundum.  The 
gelatine  and  the  benzoic  acid  were  completely  oxidized, 
but  the  silundum  was  unattacked. 


(16) 


ACTION  OF  FUSED  SALTS,  ETC. — Silundum  is  not 
decomposed  by  the  following  fused  salts:  sodium  sili- 
cate, borax,  a  mixture  of  potassium  ahlorate  and 
potassium  nitrate,  potassium  acid  sulfate,  cryolite, 
potassium  dichromate. 

Silundum  is  decomposed  by  fused  sodium  carbonate, 
sodium  hydroxide,  and  potassium  hydroxide  in  pres- 
ence of  air,  yielding  the  corresponding  silicates  and 
carbon  dioxide. 

ACTION  OF  ACIDS — Silundum  is  not  acted  upon  by 
hydrochloric,  nitric,  or  sulfuric  acids,  nor  by  a  mixture 
of  hydrochloric  and  nitric  acids,  a  mixture  of  chromic 
and  sulfuric  acids,  nor  by  fused  boric  acid.  Com- 
mercial silundum,  however,  is  slightly  attacked  by 
hydrofluoric  acid  and  by  a  mixture  of  nitric  and  hydro- 
fluoric acids,  because  of  the  presence  of  free  silicon  and 
silicon  dioxide;  but  pure  samples  of  silundum  are  not 
attacked  by  these  acids. 

ACTION  OF  OTHER  SUBSTANCES — Molten  sulfur  has 
no  action  on  silundum.  Sodium  peroxide  oxidizes 
it  to  sodium  silicate  plus  sodium  carbonate.  Lead 
oxide  also  oxidizes  it,  producing  metallic  lead  and  car- 
bon dioxide  (pp.  566  and  570).  Fused  sodium  in  pres- 
ence of  air  decomposes  silundum,  yielding  sodium 
silicate  and  sodium  carbonate.  The  action  in  this 
case  is  most  likely  due  to  the  presence  of  sodium  per- 
oxide formed  from  the  sodium. 

COMPOSITION    OF    SILUNDUM' 

In  order  to  obtain  silundum  as  pure  as  possible 
for  analysis,  graphite  rods  were  silundumized  accord- 
ing to  the  previously  described  methods,  in  a  charge 
consisting  of  sugar-carbon  and  precipitated  silica. 
The  resulting  silundum  was  broken  up  into  small 
pieces  in  a  steel  mortar,  and  subsequently  ground  to 
a  very  fine  powder  in  an  agate  mortar.  The  powder 
was  then  purified.  Depending  upon  the  conditions 
of  preparation,  the  product  obtained  was  either  silicon 
carbide  or  silicon  oxycarbide,  with  probable  impurities 
either  from  the  charge  or  from  the  reaction,  or  from 
the  mortar  in  which  the  material  was  ground.  The 
impurities  may  be  silicon,  silica,  carbon,  and  iron. 
Silicon  was  removed  with  boiling  potassium  hydroxide 
solution,  any  remaining  silica  by  means  of  hydro- 
fluoric acid,  and  the  uncombined  carbon  by  long  oxida- 
tion with  a  strong  blast  lamp.  Finally,  in  order  to 
assure  complete  oxidation  the  material  was  boiled 
with  chromic  and  sulfuric  acids,  and  then  with  hydro- 

(17) 


chloric  acid  in  order  to  remove  any  particles  of  iron 
which  may  have  been  abraded  from  the  mortar. 
The  material  was  then  thoroughly  washed,  and  when 
dried  was  ready  for  analysis. 

For  the  silicon  determination  0.3  to  0.4  g.  of  the 
above  purified  substance  was  weighed  into  a  platinum 
crucible.  To  this  were  added  4  g.  of  chemically  pure 
sodium  carbonate  and  a  small  crystal  of  potassium 
nitrate.  The  contents  were  then  well  mixed  and  the 
covered  crucible  heated,  great  caution  being  used  to 
avoid  spattering.  The  heating  was  continued  until 
a  quiet  fusion  resulted,  then  strongly  increased  until 
all  the  carbon  particles  were  oxidized,  leaving  a  clear 
melt.  This  upon  cooling  gave  a  clear,  white  mass, 
which  was  dissolved  in  hydrochloric  acid  and  evapo- 
rated to  dryness,  dehydrated  three  times,  and  the  de- 
termination of  silica  made  as  in  rock  analysis.  The 
silica  was  weighed  by  difference  after  repeated  evapora- 
tion with  hydrofluoric  acid.  Duplicate  analyses 
checked  within  0.15  per  cent.  From  the  amount  of 
silica  obtained  the  percentage  of  silicon  was  calculated. 
The  results  are  given  in  Table  V. 

TABLE  V — ANALYSES  OF  SILUNDUM  FOR  SILICON 

PER  CENT  SILICON  FOUND  THEORETICAL  PER  CENT  SILICON 
Steel-gray              Slate-gray  in  silicon  in 

silundum  silundum  carbide  SJ4C4O 

69.46  63.16  70.22  63.88 

69.59  63.28 

The  method1  formerly  employed  for  the  determina- 
tion of  combined  carbon  in  carborundum-like  sub- 
stances was  to  fuse  about  0.3  g.  of  the  substance  with 
3  g.  of  calcined  magnesium  oxide  and  6  g.  of  sodium 
peroxide  in  a  nickel  crucible.  A  blank  test  had  to 
be  run  at  each  set  of  experiments  to  determine  the 
amount  of  carbon  dioxide  present  in  the  magnesia  and 
sodium  peroxide.  Furthermore,  it  was  necessary  to 
heat  the  crucible  with  a  hydrogen  flame  until  a  vigor- 
ous reaction  occurred,  and  the  crucible  while  still  hot 
was  transferred  to  a  desiccator  charged  with  soda- 
lime  and  allowed  to  cool.  The  carbon  dioxide  was  then 
determined  by  any  suitable  method. 

This  scheme  is  subject  to  grave  error,  owing  to  the 
appreciable  amounts  of  carbon  dioxide  present  in  the 
magnesia  and  sodium  peroxide.  The  carbon  dioxide 
content  of  the  sodium  peroxide  continually  increases, 
and  therefore,  even  with  the  blank  corrections,  the  re- 
sults are  subject  to  error.  The  reaction  is  generally 
so  violent  that  spattering  is  almost  unavoidable. 

1  Fitzgerald,  Loc.  cit. 

(18) 


Moreover,  the  process  is  long,  and  involves  too  many 
operations  to  yield  absolutely  quantitative  results 
under  the  conditions  given. 

The  method  worked  out  in  this  paper  avoids  these 
difficulties. 

After  preliminary  experiments  with  various  oxides, 
such  as  pure  cupric  oxide,  ferric  oxide,  and  manganese 
dioxide,  as  oxidizing  agents,  it  was  found  that  only 
molten  litharge  gave  good  results  on  carbon  determina- 
tions in  carborundum-like  substances.  Molten  litharge 
disintegrates  the  particles  of  silundum,  and  at  the  same 
time  oxidizes  the  carbon  to  carbon  dioxide.  The  re- 
actions may  be  written  as  follows: 

SiC  +  4PbO — ^SiO2  +  4?b  +  CO2r 

PbO  +  Si02 — >PbSiO3,  and  2Pb  +  O2 — >  2PbO. 


V-  Co>r\bu»nof\ 
C\-  H.  £o4 
K-    H»60« 
K-  CO,  /b«orbTiofi 


- Yomer  "Typa. 


FIG.  4 


PROCEDURE — 0.20  to  0.25  g.  of  the  sample  was 
weighed  out  in  a  watch  glass.  This  was  thoroughly 
mixed  with  5  g.  of  litharge  whose  carbon  dioxide 
content  had  been  determined  in  a -blank  test  carried 
out  under  the  same  conditions  as  the  analysis.  The 
mixture  of  litharge  and  sample  was  placed  in  a  C.  M. 
Johnson  combustion  boat  made  of  vitrified  clay, 
120  mm.  long  and  15  mm.  wide.1  Experiments  were 
also  made  with  combustion  boats  of  porcelain,  alun- 
dum,  nickel,  iron,  and  copper,  but  all  except  the  vitri- 
fied clay  were  attacked  and  fused  by  the  molten  litharge. 

The  boat  with  its  charge  was  placed  in  the  silica 
tube  of  an  electric  combustion  furnace,  and  the  air 
in  the  furnace  displaced  by  oxygen  that  had  been 
thoroughly  dried  in  a  drying  train.  The  current  was 


Eimer  and  Amend,  New  York 


(19) 


turned  on  and  the  temperature  raised  slowly  enough 
to  avoid  too  rapid  decomposition,  which,  if  it  occurred, 
would  blow-  the  charge  out  of  the  combustion  boat. 
A  gentle  stream  of  oxygen  was  passed  through  the  ap- 
paratus throughout  the  determination,  and  the  course 
of  the  reaction  was  followed  by  observing  the  rate  at 
which  the  bubbles  of  gas  passed  through  the  absorp- 
tion apparatus.  As  soon  as  the  evolution  of  carbon 
dioxide  tended  to  become  rapid,  the  electric  current 
and  the  flow  of  oxygen  were  turned  off  until  the  reaction 
subsided,  and  no  more  bubbles  of  gas  passed  through 
the  absorption  apparatus.  Then  the  current  was 
turned  on  again,  and  a  slow  stream  of  oxygen  passed 
through.  The  temperature  inside  the  furnace  was 
kept  at  about  600°  C.  for  about  45  minutes,  and  then 
gradually  raised  to  about  1000°.  This  was  done  to 
eliminate  any  possibility  of  carbon  dioxide  remaining 
in  the  molten  mass.  The  carbon  monoxide  that  may 
be  given  off  at  this  temperature  is  converted  into 
carbon  dioxide  by  passing  over  a  heated  coil  of  cupric 
oxide.  The  carbon  dioxide  evolved  was  absorbed  in 
a  Vanier  KOH  absorption  apparatus. 

The  arrangement  of  the  apparatus  as  set  up  is  indi- 
cated in  Fig.  4.  Analyses  made  by  this  method  are 
given  in  Table  VI. 

TABLE  VI — CARBON  IN  CARBORUNDUM  AND  SILUNDUM 
Correction  for  CO2  in  PbO  =  0.0175  Gram 

Theo- 

Weight     Grams    Weight  Per  cent   retical 
Sample       COz  COz          C  in     Per  cent 

SAMPLE  Grams    evolved  corrected  sample  Carbon 

Large  carborundum  crystal,.  {0.2004     0.2330     0.2155     29.33     tafflC 

(0.2509  0.2925  0.2750  29.89  in 

Steel-gray  silundum ^0.2214  0.2609  0.2434  29.95  SiC 

/  0.2187  0.2586  0.2393  29.84  29.78 

(0.2082  0.2308  0.2133  27.94  in 

Slate-green  silundum ^0.2413  0.2633  0.2458  27.76  Si^O 

i 0.2265  0.2488  0.2313  27.85  27.09 

From  the  examination  of  the  data  in  Tables  V  and 
VI  as  summarized  in  Table  VII,  it  is  evident  that 
the  percentage  of  carbon  and  the  percentage  of  silicon 
in  the  steel-gray  variety  of  silundum  add  up  nearly 
to  100  per  cent,  indicating  that  the  accepted  formula 
SiC  is  .correct  for  this  modification  or  variety.  On 
the  other  hand  the  silicon  and  carbon  in  the  slate- 
green  variety  of  silundum  add  up  to  only  91.07  per 
cent.  This  variety  evidently  does  not  correspond  to 
the  formula  SiC. 

It  may  be  assumed  from  the  careful-  method  of 
preparation,  in  which  only  pure  silica,  sugar-carbon, 
and  graphite  were  used,  that  the  compound  can  con- 

(20) 


tain  only  silicon,  carbon,  and  oxygen.  Since  a  tempera- 
ture of  approximately  1600°  C.  must  be  attained  for 
the  reaction  to  begin,  practically  all  the  air  is  expelled 
from  the  covered  crucible;  and  further,  since  carbon 
monoxide  gas  is  formed  by  the  reaction  and  sweeps 
out  the  last  traces  of  air,  the  reaction  product  can  con- 
sist only  of  carbon,  silicon,  and  oxygen,  and  their 
compounds.  The  remaining  8.93  per  cent  may  legiti- 

TABI/E  VII — SUMMARY  OF  ANALYSES 

Carbo-  Steel-gray       Slate-green 

rundum  silundum          silundum 

PER  CENT  FOUND  {  |i;  •  •  •  • ;  •  ^  ^  69 .  5g3  63  22 


TOTAL 99.42  91.07 

Silicon  carbide      Si4C4<D 
PER  CENT  THEORETICAL  {  f?; ; ; ; ; ; ; ;     29 ;  ^  ™ .  22  63 . 88 

TOTAL 100.00  90.97 

mately  be  assumed  to  be  oxygen.  The  percentage  of 
oxygen  corresponding  to  the  formula  Si4C4O  is  9.03 
per  cent;  oxygen  by  difference  is  8.93  per  cent,  which 
is  good  agreement. 

Attempts  were  made  to  determine  the  oxygen  con- 
tent of  the  slate-green  variety  directly.  The  sample 
was  placed  with  a  pure  metal,  such  as  lead,  steel, 
or  copper  in  a  vitrified  clay  boat  in  a  combustion 
tube  of  a  platinum-wound  electric  furnace,  in  which 
a  temperature  of  1300°  C.  can  be  easily  attained. 
The  air  in  the  apparatus  was  displaced  by  extremely 
carefully  purified  nitrogen,  prepared  from  ammonium 
nitrite.  The  idea  in  view  was  that  the  molten  metal 
would  dissolve  the  substance  and  carbon  monoxide 
or  carbon  dioxide  might  be  liberated.  Arrangement 
was  made  for  the  monoxide  to  be  oxidized  to  dioxide 
by  passing  through  a  hot  tube  containing  cupric  oxide. 
Owing  to  the  fact  that  the  sample  in  each  case  floated 
on  the  surface  of  the  molten  metal,  no  reaction  oc- 
curred, as  evidenced  by  the  fact  that  the  KOH  ab- 
sorption apparatus  did  not  gain  in  weight. 

As  regards  the  relationship  of  silundum  to  car- 
borundum, results  obtained  in  this  paper  indicate  that 
the  steel-gray  variety  is  a  form  of  carborundum.  The 
following  facts  may  be  mentioned: 

i — Silundum  has  the  same  chemical  composition  as 
carborundum. 

2 — Their  chemical  properties  are  similar. 

3 — The  temperatures  of  formation  and  decomposi- 
tion are  practically  the  same. 

(21) 


4 — Some  of  the  physical  properties  measured  vary 
from  those  given  in  the  literature.1  This  difference 
most  likely  is  due  to  the  fact  that  the  other  workers 
used  different  methods  for  their  measurements. 

SUMMARY 

I — Two  distinct  varieties  of  silundum  were  prepared, 
i — The   slate-green   variety:   formula  Si4C40. 
2 — The  steel-gray  variety:  formula  SiC. 

II — Experiments  were  made  to  determine  the  effect 
of  varying  the  temperature,  duration  of  heating,  and 
composition  of  charge. 

Ill — The  temperatures  of  formation  and  decomposi- 
tion of  the  two  varieties  of  silundum  were  determined. 

IV — The  physical  and  chemical  properties  of  both 
forms  of  silundum  were  investigated. 

V — Results  obtained  in  this  investigation  tend  to 
show  that  the  steel-gray  variety  of  silundum  is  a  va- 
riety of  carborundum. 

VI — A  quantitative  method  for  carbon  determina- 
tion in  carborundum-like  substances  has  been  devised. 

ELECTROCHEMICAL  LABORATORY 
COLUMBIA  UNIVERSITY,  NEW  YORK  CITY 


1  Pamphlet,    "Chemical   and    Physical    Properties   of  Carborundum," 
published  by  The  Carborundum  Co.,  Niagara  Falls.  N.  Y..    1913. 


(22) 


BIBLIOGRAPHY 

F.  Boiling:  Chemiker  Zeit.,  32,  1104. 

F.  Boiling:  Electro- Chem.  and  Met.  Ind.,  7,  24. 

Moyat:  Chemiker  Zeit.,  32,  1166. 

Acheson:  Electrochem.  and  Met.  Ind.,  6,  379. 

Acheson:  U.  S.  Patent  No.  895,531. 

Tucker,  Kudlich,  Heumann:  Trans.  Amer.  Electro-chem. 
Soc.,  16,  207. 

Amberg-Bodio :  Electrochemie,   15,  725-727;  C.  A.,  4,   149. 

Tone:  U.  S.  Patents  No.  913,324;  992,698;  1,013,701;  1,013,700. 

Egly:  Electrotechnische  Zeitschrift,  34,  263-267;  C.  A.,  6, 
536;  7,  1142;  7,  2357. 

F.  J.  Tone:  Trans.  Amer.  Electro-chem.  Soc.,  26,  181. 

Fitzgerald:  Electro-chem.  Industry,  2,  443. 

Arsem:  Trans.  Amer.  Electro-chem.  Soc.,  9,  153. 

Tucker:  Trans.  Amer.  Electro-chem.  Soc.,  n,  307. 

Metal  Industry,  November,  1914,  457. 

Spielman:  J.  S.  C.  I.,  24,  654. 

Electrical  World,  53,  174. 

Electrical  Review,  63,   1070;  C.  A.,  3,  286. 

L'Electricien,  37,  214. 

Fitzgerald:  Electro-chem.  and  Met.  Ind.,  3,  459-463; 
Chemische-Industrie,  36,  304-308. 

Grossmann:  Elektrotechnische  Zeitschrift,  1909,  pp.  165, 
789. 

Pamphlet:  "Chemical  and  Physical  Properties  of  Carbo- 
rundum," published  by  the  Carborundum  Co.,  Niagara  Falls, 
N.  Y.,  1913- 


VITA 

Alexander  Lowy  was  born  on  March  31,  1889. 
He  received  his  early  education  in  the  New  York  City 
public  schools.  He  attended  the  College  of  the  City 
of  New  York  from  1905  to  1910.  He  received  the 
degree  of  B.S.  from  Columbia  University  in  1911. 
During  the  year  1911—1912  he  pursued  graduate  work 
in  Chemistry  there,  and  received  the  degree  of  M.A. 
in  1912;  the  thesis  for  the  M.A.  degree  was  in  organic 
chemistry.  In  the  same  year  he  was  awarded  a  Uni- 
versity Scholarship  in  organic  chemistry.  In  1912 
he  was  appointed  laboratory  assistant  in  Electro- 
chemistry. During  the  summer  of  1913  and  1914  he  was 
chemist  for  the  City  of  New  York.  From  1911  to 
the  present  time  he  has  studied  under  the  Faculty  of 
Pure  Science  of  Columbia  University  for  the  degree 
of  Doctor  of  Philosophy. 


••••••••••••I 


FOURTEEN  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 


This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 
Renewed  books-are  subject  to  immediate  recall. 


r5Majr56£C 


MAY7"195SLU 


5  1995 


y*+-d£ 


LD  21-100m-2,'55 
(B139s22)476 


Gt 

Universe 
Bt 


YC   18385 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


